The most important mechanism of microbial resistance to xcex2-lactam antibiotics is the bacterial production of xcex2-lactamases, enzymes which hydrolytically destroy xcex2-lactam antibiotics, such as penicillins and cephalosporins. This type of resistance can be transferred horizontally by plasmids that are capable of rapidly spreading the resistance, not only to other members of the same strain, but even to other species. Due to such rapid gene transfer, a patient can become infected with different organisms, each possessing the same xcex2-lactamase.
xcex2-lactamase enzymes have been organized into four molecular classes: A, B, C, and D based on amino acid sequence. Class A, which includes RTEM and the xcex2-lactamase of Staphylococcus aureus, class C, which includes the lactamase derived from P-99 Enterobacter cloacae, and class D are serine hydrolases. Class A enzymes have a molecular weight of about 29 kDa and preferentially hydrolyze penicillins. The class B lactamases are metalloenzymes and have a broader substrate profile than the proteins in the other classes. Class C enzymes include the chromosomal cephalosporinases of Gram-negative bacteria and have molecular weights of approximately 39 kDa. The recently recognized class D enzymes exhibit a unique substrate profile which differs significantly from both class A and class C.
The class C cephalosporinases, in particular, are responsible for the resistance of gram negative bacteria to a variety of both traditional and newly designed antibiotics. The Enterobacter species, which possesses a class C enzyme, is now the third greatest cause of nosocomial infections in the United States. This class of enzymes often has poor affinities for inhibitors of the class A enzymes, such as clavulanic acid, a commonly prescribed inhibitor, and to common in vitro inactivators, such as 6-xcex2-iodopenicillanate.
One strategy for overcoming this rapidly evolving bacterial resistance is the synthesis and administration of xcex2-lactamase inhibitors. Frequently, xcex2-lactamase inhibitors do not possess antibiotic activity themselves and are thus administered together with an antibiotic. One example of such a synergistic mixture is the product sold under the trademark AUGMENTIN (amoxicillin, clavulanate potassium), which contains the antibiotic amoxicillin and the xcex2-lactamase inhibitor, clavulanate potassium.
There is a continued need for novel xcex2-lactamase inhibitors, and in particular, for xcex2-lactamase inhibitors that can be coadministered with a xcex2-lactam antibiotic.
The invention provides a compound of formula I: 
wherein:
R1, R2, R5, and R6 are each independently hydrogen, (C1-C10)alkyl, (C2-C10)alkenyl, (C2-C10)alkynyl, (C3-C8)cycloalkyl, (C1-C10)alkoxy, (C1-C10)alkanoyl, (C1-C10)alkanoyloxy, (C1-C10)alkoxycarbonyl, aryl, heterocycle, halo, cyano, nitro, xe2x80x94COORa, xe2x80x94C(xe2x95x90O)NRbRc, xe2x80x94OC(xe2x95x90O)NRbRc, NRbRc, or xe2x80x94S(O)nRd; or R1 and R2 together with the carbon to which they are attached are (C3-C8)cycloalkyl or a heterocycle, wherein each (C3-C8)cycloalkyl or heterocycle is optionally substituted with (C1-C10)alkyl, hydroxy, halo, (C1-C10)alkoxy, (C1-C10)alkanoyloxy, or (C1-C10)alkoxycarbonyl; or R5 and R6 together with the carbon to which they are attached are (C3-C8)cycloalkyl or a heterocycle, wherein each (C3-C8)cycloalkyl or heterocycle is optionally substituted with (C1-C10)alkyl, hydroxy, halo, (C1-C10)alkoxy, (C1-C10)alkanoyloxy, or (C1-C10)alkoxycarbonyl;
R3 is hydrogen, (C1-C10)alkyl, (C2-C10)alkenyl, (C2-C10)alkynyl, (C3-C8)cycloalkyl, (C1-C10)alkoxy, (C1-C10)alkanoyl, (C1-C10)alkanoyloxy, (C1-C10)alkoxycarbonyl, halo, cyano, nitro, aryl, heterocycle, xe2x80x94COORa, xe2x80x94C(xe2x95x90O)NRbRc, xe2x80x94OC(xe2x95x90O)NRbRc, NRbRc, or xe2x80x94S(O)nRd;
R4 is hydrogen;
A is thio (S), sulfinyl (SO), or sulfonyl (SO2);
each n is independently 0, 1, or 2;
each Ra is independently hydrogen, or (C1-C10)alkyl;
each Rb and Rc is independently hydrogen, (C1-C10)alkyl, (C1-C10)alkoxy, phenyl, benzyl, phenethyl, or (C1-C10)alkanoyl;
each Rd is independently (C1-C10)alkyl, (C1-C10)alkanoyl, aryl, heterocycle, aryl(C1-C6)alkyl, heterocycle, or heterocycle(C1-C6)alkyl;
wherein any (C1-C10)alkyl, (C2-C10)alkenyl, (C2-C10)alkynyl, (C3-C8)cycloalkyl, (C1-C10)alkoxy, (C1-C10)alkanoyl, (C1-C10)alkanoyloxy, or (C1-C10)alkoxycarbonyl of R1, R2, R3, R5, and R6 is optionally substituted with one or more (e.g. 1, 2, 3, or 4) substituents independently selected from halo, hydroxy, cyano, cyanato, nitro, mercapto, oxo, aryl, heterocycle, (C2-C6)alkenyl, (C2-C6)alkynyl, (C1-C6)alkoxy, (C1-C6)alkanoyl, (C1-C6)alkanoyloxy, aryl(C1-C6)alkanoyloxy, halo(C1-C6)alkanoyloxy, heterocycle(C1-C6)alkanoyloxy, aryloxy, (heterocycle)oxy, xe2x80x94COORa, (C3-C8)cycloalkyl, xe2x80x94C(xe2x95x90O)NRbRc, xe2x80x94OC(xe2x95x90O)NRbRc, NRbRc, and xe2x80x94S(O)nRd; and
wherein any aryl is optionally substituted with one or more (e.g. 1, 2, 3, or 4) substituents independently selected from halo, hydroxy, cyano, trifluoromethyl, nitro, trifluoromethoxy, (C1-C6)alkyl, (C1-C6)alkanoyl, (C1-C6)alkanoyloxy, (C1-C6)alkoxycarbonyl, xe2x80x94COORa, xe2x80x94C(xe2x95x90O)NRbRc, xe2x80x94OC(xe2x95x90O)NRbRc, NRbRc, and xe2x80x94S(O)nRd;
or a pharmaceutically acceptable salt thereof.
The invention also provides a compound of formula IV: 
wherein:
R7 and R8 are each independently hydrogen, (C1-C10)alkyl, (C2-C10)alkenyl, (C2-C10)alkynyl, (C3-C8)cycloalkyl, (C1-C10)alkoxy, (C1-C10)alkanoyl, (C1-C10)alkanoyloxy, (C1-C10)alkoxycarbonyl, aryl, heterocycle, halo, cyano, nitro, xe2x80x94COORe, xe2x80x94C(xe2x95x90O)NRfRg, xe2x80x94OC(xe2x95x90O)NRfRg, NRfRg, or xe2x80x94S(O)nRh;
R9 is cyano, xe2x80x94CHxe2x95x90NORi, or a radical of the following formula 
R10 is hydrogen;
A is thio, sulfinyl, or sulfonyl;
each n is independently 0, 1, or 2;
each Re is independently hydrogen, or (C1-C10)alkyl;
each Rf and Rg is independently hydrogen, (C1-C10)alkyl, (C1-C10)alkoxy, phenyl, benzyl, phenethyl, or (C1-C10)alkanoyl;
each Rh is independently (C1-C10)alkyl, phenyl, aryl(C1-C6)alkyl, heterocycle, or heterocycle(C1-C6)alkyl;
Ri is hydrogen or (C1-C6)alkyl; and
Rj and Rk are each independently hydrogen, halo, cyano, nitro, aryl, heterocycle, (C2-C6)alkenyl, xe2x80x94COORe, xe2x80x94C(xe2x95x90O)NRfRg, xe2x80x94OC(xe2x95x90O)NRfRg, NRfRg, or xe2x80x94S(O)nRh;
wherein any (C1-C10)alkyl, (C2-C10)alkenyl, (C2-C10)alkynyl, (C3-C8)cycloalkyl, (C1-C10)alkoxy, (C1-C10)alkanoyl, (C1-C10)alkanoyloxy, or (C1-C10)alkoxycarbonyl of R7, R8, Rj and Rk is optionally substituted with one or more (e.g. 1, 2, 3, or 4) substituents independently selected from halo, hydroxy, cyano, cyanato, nitro, mercapto, oxo, aryl, heterocycle, (C2-C6)alkenyl, (C2-C6)alkynyl, (C1-C6)alkoxy, (C1-C6)alkanoyl, (C1-C6)alkanoyloxy, aryl(C1-C6)alkanoyloxy, halo(C1-C6)alkanoyloxy, heterocycle(C1-C6)alkanoyloxy, aryloxy, (heterocycle)oxy, (C3-C8)cycloalkyl, xe2x80x94COORe, xe2x80x94C(xe2x95x90O)NRfRg; xe2x80x94OC(xe2x95x90O)NRfRg, NRhRi, or xe2x80x94S(O)nRk; and
wherein any aryl is optionally substituted with one or more (e.g. 1, 2, 3, or 4) substituents independently selected from halo, hydroxy, cyano, trifluoromethyl, nitro, trifluoromethoxy, (C1-C6)alkyl, (C1-C6)alkanoyl, (C1-C6)alkanoyloxy, (C1-C6)alkoxycarbonyl, xe2x80x94COORe, xe2x80x94C(xe2x95x90O)NRfRg, xe2x80x94OC(xe2x95x90O)NRfRg, NRhRi, or xe2x80x94S(O)nRk;
or a pharmaceutically acceptable salt thereof.
The invention also provides a pharmaceutical composition comprising a compound of formula I or IV, or a pharmaceutically acceptable salt thereof, in combination with a pharmaceutically acceptable diluent or carrier, as well as such a pharmaceutical composition that further comprises a xcex2-lactam antibiotic.
The invention also provides a method comprising inhibiting a xcex2-lactamase by contacting (in vitro or in vivo) the xcex2-lactamase with an effective amount of a compound of formula I or IV; or a pharmaceutically acceptable salt thereof.
The invention also provides a therapeutic method comprising inhibiting a xcex2-lactamase in a mammal in need of such therapy, by administering an effective inhibitory amount of a compound of formula I or IV; or a pharmaceutically acceptable salt thereof.
The invention also provides a method comprising enhancing the activity of a xcex2-lactam antibiotic, by administering the xcex2-lactam antibiotic to a mammal in need thereof, in combination with an effective xcex2-lactamase inhibiting amount of a compound of formula I or IV; or a pharmaceutically acceptable salt thereof.
The invention also provides a method comprising treating a xcex2-lactam resistant bacterial infection in a mammal, by administering an effective amount of a xcex2-lactam antibiotic in combination with an effective xcex2-lactamase inhibiting amount of a compound of formula I or IV; or a pharmaceutically acceptable salt thereof.
The invention also provides a compound of formula I or IV for use in medical therapy (preferably for use in inhibiting a [-lactamase in a mammal, or for treating a xcex2-lactam resistant bacterial infection in a mammal), as well as the use of a compound of formula I or IV for the manufacture of a medicament useful for inhibiting a xcex2-lactamase in a human.
The invention also provides processes and intermediates disclosed herein that are useful for preparing xcex2-lactamase inhibitors of formula I or IV.
Compounds of formula I and IV are useful as xcex2-lactamase inhibitors for therapeutic applications. They are also useful as pharmacological tools for in vitro or in vivo studies to investigate the mechanisms of antibiotic resistance, to help identify other therapeutic antibiotic agents or xcex2-lactamase inhibitors, to identify which xcex2-lactamases are being expressed by a given microorganism, or to selectively inhibit one or more xcex2-lactamases in a microorganism.